In information theory, a low-density parity-check (LDPC) code is an error correcting code for transmitting a message over a noisy transmission channel. LDPC codes are a class of linear block codes. While LDPC and other error correcting codes cannot guarantee perfect transmission, the probability of lost information can be made as small as desired. LDPC was the first code to allow data transmission rates close to the theoretical maximum known as the Shannon Limit. LDPC was impractical to implement when developed in 1963.
Turbo codes, discovered in 1993, became the coding scheme of choice in the late 1990s. Turbo codes are used for applications such as deep-space satellite communications. In modern modems designed for emerging high bit rate cellular standards such as Long Term Evolution (LTE) and LTE advanced (LTE/ADV), Turbo decoders pose the highest design complexity and consume the most power.